Bioreactor optimization and characterization of thermostable amylolytic enzymes from Bacillus stearothermophilus GRE1 | |
| Author | Hossain, S. M. Zakir |
| Call Number | AIT Thesis no.BT-03-20 |
| Subject(s) | Bioreactors Enzymes Amylases |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. BT-03-20 |
| Abstract | Optimum production of extracellular, thermostable amylolytic enzyme (a. and P-amylase) by a newly isolated microorganism identified as Bacillus stearothermophilus GREl was investigated in batch reactor. 1.0 % (w/v) starch and 3.0 % (w/v) lactose were found to be optimal by single factor experiment for enzyme production. Mathematical model developed using response surface methodology also revealed that 1.02% starch and 3.12% lactose produced the best effect on the production of enzymes. Optimum enzyme production condition (neutral pH and incubation temperature of 45°C) resulted 0.64 h-1 of specific growth rate, 2.20 g/l of biomass, 11.43 U/ml a.-amylase and 10.04 U/ml of Pamylase. In addition, enzyme production was growth-associated both in shake flask and bioreactor studies. Amylase activity increased 5-6 fold in the bioreactor as compared to the shake flask culture. Native wheat, cassava, corn and potato starch granules were hydrolyzed using the crude enzyme and showed a percentage degradation rate values ranging from 80% to 60% at 60°C with potato starch the least degraded and wheat starch with the highest value after 36 hours of incubation. At 40°C only 30% of potato starch was hydrolyzed. At 60°C the range of the percentage degradation rate using the partially purified enzyme however, was 63 to 50%. Km and Vmax values of the crude enzyme which were calculated from the Lineweaver-Burk plot, were 5 .5 mg starch/ml and 3 7 .0 mg reducing sugar/min, respectively while that of the partially purified enzyme was determined to be 5.0 mg starch/ml and 42.0 mg reducing sugar/min. On the other hand, the melting temperature and %GC content of the genomic DNA of the organism were 86°C and 41 % respectively. Overall the thermostable enzyme obtained from the screened B. strearothermophilus GREl organism was able to produce enzyme in large quantities in the bioreactor. The characteristics of the enzyme indicate that it is able to react with granular starch at subgelatinization temperature. |
| Year | 2003 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. BT-03-20 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Rakshit, Sudip Kumar; |
| Examination Committee(s) | Vinod K. Jindal;Athapol Noomhorm; |
| Scholarship Donor(s) | The Government of Netherlands; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2003 |